1. Field of the Invention
The invention relates to an electromechanical abutment sensor, particularly for folding machines, which includes parts which are movable resiliently relative to each other, said parts comprising a coil and a magnet, preferably a permanent magnet.
2. Description of the Prior Art
In the folding mechanisms of folding machines, the sheets which are to be folded are fed towards an abutment located transversely to the direction of infeed of the sheets. As soon as a sheet which is to be folded has reached its position of rest in front of the abutment, the drive for the folding blade is switched on and the sheet is folded by means of the folding blade. In order to trigger the blade drive, a sensor must be provided which switches on the blade drive as rapidly as possible once the leading edge of the sheet has reached the abutment.
It is known for example from DOS No. 30 22 607 to detect the leading edge of the sheet by means of a light barrier located a certain distance in front of the abutment. In this case, though, an electronic delay and monitoring circuit must be provided to ensure that the blade drive is not switched on before the leading edge of the sheet has reached the abutment. For reasons of space, location of the light barrier directly at the abutment presents difficulty.
It would be more favourable to provide directly at the abutment a sensor which reacts to the pulse from the sheet striking the abutment. Suitable for this are electromechanical abutment sensors which give out an electrical signal in response to a mechanical pulse. The known electromechanical sensors, for example of the type known from U.S. Pat. No. 3,739,204, are however of considerable overall height so that a corresponding depth must be allowed for in order to install them.
The invention is therefore based on the problem of providing an electromechanical abutment sensor which is of the lowest possible installation height.